![]() ![]() Redundancy and system reliability have traditionally far outweighed any concerns over minor efficiency losses. The age of the boiler, steam trap maintenance, and steam leaks all contribute to making the actual efficiencies of these systems much lower. The inherent design of these boilers as noncondensing limits their efficiency, even in ideal conditions. Field-built water-tube boilers and manufactured water- and fire-tube boilers from 500 to 2,000 hp or more are present at most large hospital campuses. This makes the steam system a major component of the facility, requiring trained and experienced boiler operators. Domestic hot water and heating hot water are generated with steam using shell and tube or tank bundle-type steam converters. These additional building functions can include kitchen, laundry, and typically all water heating. Historically, the steam system has been used to serve all functions requiring heat. Because a steam system is necessary to begin with, there is a tendency to make it support a host of building functions. Hospitals, especially large ones (>500,000 sq ft), have an inherent steam requirement for sterilization-related equipment and the humidification of large outside air quantities. Coupled with the fact that domestic hot-water uses are constant throughout the year, a typical hospital may have a summer water-heating load that is two-thirds of the winter hot-water-heating load. This results in the need for reheat all year. A portion of the terminal units is actually designed as constant volume terminal units, because the minimum airflow requirement exceeds the airflow required to meet both the heating and cooling load of the spaces. When a VAV system is used in a health care facility project, the minimum airflow of the terminals is dictated by the space’s minimum airflow requirements. The majority of the health care facilities built within the last 20 years use a VAV system with hot-water reheat therefore, this article will use this type of system as a basis for discussion. In recent years, newer systems have been developed and tested including variable refrigerant flow systems and chilled beams. Different systems have been used over the decades to meet these requirements, including constant-volume single zone, constant-volume multizone, dual-duct systems, and single-duct variable air volume (VAV) systems. ![]() The codes also dictate the amount of air that is fresh outside air. All of the health care HVAC-related codes concentrate on the minimum acceptable airflow quantities for each type of space and the pressure relationship between the spaces. The Facility Guidelines Institute’s (FGI) Guidelines for Design and Construction of Hospitals and Outpatient Facilities” is the primary guideline being used today for hospital accreditation by The Joint Commission, and many states have either their own amendments or a complete alternate code.įGI now references ASHRAE Standard 170: Ventilation of Health Care Facilities for the actual airflow requirements. Many of the spaces have minimum airflows regardless of the actual loads or the number of occupants. More than any other building type, airflow quantities in a hospital are dictated by code. ![]()
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